GSXR and Bandit Alternator overcharging problems.
First some theory:
Suzuki have tried to be clever using a closed loop design which may work when everything is new perhaps.
Out of alternator are two leads the main power to battery and the other is the ignition feed to alternator which is trigger to turn reg on.
Problem here is voltage drop on the trigger wire, ive measured half volt purely at ignition switch, suppose age takes its toll. ive got further .3 volt loss through wiring and joints i can tell you the connectors are clean and look good.
So alternator battery lead reads say 12.6 volts (engine off) ignition lead reads 12.5 volts but lights on this drops to 11.5 volts where the battery lead reads 12.3 a drop of .8 through switch and harness, so when running when lights are turned on alternator compensator by ramping up output to 15.4 volts which cooks the battery.
Solution.
Remove ignition feed wire to the alternator and use it to power a relay (switch side) the ignition wire out of alternator straight to positive on battery via the new relay.
Result constant 14.3 volts depending on battery state no matter whats on or off, result.
You have to connect via a relay as the reg would drain the battery in no time as this is trigger to turn reg side of circuit on as its a basic deign not like car 1 wire systems where the actual rotation of alternator triggers it on.
That was the explanation why, now the how to:
So first of all you need to find the connector block under the rider seat shown here arrowed in green –
This has one red and one orange wire into it out of the loom and two reddish cloth covered wires out of it to the alternator. You need to cut the orange wire on the right – give yourself at least about an inch and a half of wire still coming out of the connector block, so you’ll need to open up the loom a bit. DO NOT CUT THE RED WIRE, leave it alone.
Now you need to splice in two new lengths of wire onto the cut ends. I used orange 3mm 30A rated thin wall insulation, as the closest match to the original. You don’t want to be using thinner wire than the original – thinner wire = greater resistance = voltage drop and this is the problem you are trying to cure. You can crimp the wire on, personally I prefer a soldered splice, then seal the splice with heatshrink insulation On the other end you need to crimp on female spade connectors, which to match the terminals on your relay will most likely be 6.3mm. Use double crimped ones which grip the bare wire and the insulation. Again, as well as a crimp I like to put a bit of solder on my crimped end. I also slipped insulators on the wire to cover the blades to make everything 100% weathertight.
Now you need to make up two more lengths of wire, same type as before but this time a black length and a red length. On one end of the black wire you want a double-crimped 6.4mm round battery terminal, on the other end a 6.3mm female spade with insulator. The red wire is slightly more involved as this mod bypasses the 30A circuit breaker in the original wiring, thus potentially leaving the positive feed to the trigger circuit unfused – but we’re going to sort that. You want a 30A rated waterproof inline mini blade type fuseholder, which looks like this –
The 30A rating is so that the integral wire tails it comes with will be the same rating and diameter as the rest of the wiring you are installing – again because you don’t want to introduce thinner wire into the circuit. But you want a 10A fuse in it, don’t put a 30A in it, that’s way too high for this circuit alone. On one end of one of the wire tails fit a 6.3mm female spade with insulator. Extend the other tail by splicing on extra red wire and sealing the joint with heatshrink insulation. The female spade will attach to the relay and the end of the red wire will attach to the positive terminal of the battery, so measure things out and, before attaching a double-crimped 6.4mm round battery terminal, thread it through the terminal insulator on the battery cable, as this is easier than trying to fit it through with the terminal attached. When you’ve done that attach the terminal. The new terminals sit on top of the existing battery lead terminals.
The relay I fixed to the undertray next to the fusebox as you can see. Drilled through the undertray and used a stainless nut and bolt to secure the relay bracket. I also put a bit of foam between the bracket and the undertray to provide a bit of damping but this might be overkill, as the plastic undertray is flexible anyway. I put another little bit of foam between the relay and the fusebox cover, so that is held firm and damped.
You can see in the photo below how I’ve routed the wires, so you can follow this and cut to the required length before starting. I used the groove in the undertray as a duct for them to pass underneath the fusebox, which secures them neatly. The inline fuseholder is positioned between the relay connection and before the red wiring passes underneath the fusebox, so it’s in a logical position close to the fusebox. The loom was resealed with self-amalgamating tape leaving the orange wires passing through. The red and black wires are cable tied to the battery wires, then cable tied along their length to the loom or frame. You don’t want unsecured wires flapping about, they get fatigued over the years, work harden and then you get annoying internal cracks. A tidy bike is a reliable bike 
.
So the wires go as follows – orange from the ignition switch side of the loom (i.e. from the right hand side as you’re looking at the connector block in the first photo) goes to one of the coil terminals on the relay; black wire connects to battery negative and the other coil terminal on the relay; the other orange wire, from the alternator side of the loom (i.e. from the left hand side as you’re looking at the connector block in the first photo) goes to one of the switch terminals on the relay; red wire connects to battery positive and the other switch terminal on the relay.
I think the picture below should illustrate this all clearly.
Just one thing: first i tried with a cheap relay, it had a difference of 0,2V on the switched wires, so it charged 14,7V. Then I got a better relay (no difference measurable) and it charges perfectly.
Side stand switch removal
Disclaimer – If you follow this modification it is completely at your own risk and no one other than yourself can be held accountable for any mistakes, actions or accidents which could occur from any implemented modifications and from riding in an unsafe or dangerous manner including but not restricted to, leaving side stand down whilst riding.
In other words: if you find you sometimes try to ride away with the sidestand down, don’t try this at home.
When disconnecting/removing the sidestand of your GSX-R or other oldskool Suzuki, it makes sense to remove all the unnecessary wiring and relay as well. Pic of the relay:
on Slingshot GSX-R’s it’s mounted under the battery box, on a tray together with the starter relay and circuit breaker (more about that breaker later). One orange/yellow wire comes from the fuse, this is the +12V feed to the ignition system. The orange/black wire goes to the kill switch. Connect these two wires together and you have eliminated the sidestand switch and the relay. When you rip out all the unneeded wires from the loom, you will also find a diode. Connect the blue wire (from the neutral switch) to the black/blue wire (to the neutral indicator).
Circuit breaker elimination
Under the battery box is the circuit breaker, some kind of mechanical fuse, which pops when the load is too high and can be reset by pushing back the red button. At least that’s the theory, but in practice they catch a lot of crap from the rear wheel (especially if you ride around without a rear hugger) and with age they refuse to operate in the prescribed manner. Easy sollution is to just cut it out and connect the two wires together, it works, but to be safe it’s better to install a 30A fuse instead of the circuit breaker. This fuse can be mounted in a position where it’s protected from the elements, next to the fusebox for example.
Bandit 1200 – resistor in ignition switch
The Bandit 1200 (and probably also other models) have a resistor built in the ignition switch. This prevents the bike from being started when hot-wiring it. If you want to use a B12 ignition control unit (CDI unit) in combination with anything else than a B12 ignition switch, you have to “fool” the CDI by installing a resistor in the system.
Marked in blue shows which circuit the resistor should be in:
The orange/yellow wire comes from the CDI unit and as you can see, when the lock is turned on, it is connected to black/white (ground). So just connect the orange/yellow from the CDI to ground through a 100 ohm resistor and that’s it.
By Jonny1bump, Crass and Captain Chaos.